Current magnitude-ratio responsive amplifier



CURRENT MAGNITUDE-RATIO RESPONSIVE AMPLIFIER ...nn-nu.- n n-...nu

Nov. 25, .1947. c. w. HANsELL 2,431,396

CURREN' MAGNITUDE-RATIO RESPONSIVE AMPLIFIER Filed Deo. 21, 1942 2sheets-sheet 2 TTONEY Patented Nov. 25, 1947 CURRENT MAGNITUDE-RATIORESPONSIVE AMPLIFIER Clarence W. Hansell, Port Jefferson, N. Y.,assig'nor to Radio Corporation of America, a corporation of DelawareApplication December 21, 1942, Serial No. 469,647

(Cl. Z50-27) 21 Claims.

My present invention relates to current magnitude ratio-responsiveelectron discharge devices, and more especially to amplifier circuitswhich are responsive solely to current magnitude ratios.

It has been known in the past to provide a response according to theratio of the magnitudes of two currents but the only device available,of Y which I am aware, has been a current ratio metering instrument inwhich a magnet bearing a needle is mounted inside two crossedmagnetizing coils. In this case the magnet aligns itself parallel to themagnetic field set up by currents owing through the coils. The needleindicates on a suitable scale the ratio of the currents. However, it hasnot been known howto secure an electronic current magnituderatio-responsive device.

One of the main objects of my present invention is to provide a methodof controlling the division of a current into two parts according to theratio of the magnitudes of two control currents,

I have found that when a magnetic field in a vacuum is made strongenough substantial electron motions can take place only in the directionparallel to the magnetic field. Any component of motion in otherdirections is overcome, because the magnetic field bends the path ofmotion in these directions back to the axis from which they started.Having confined the motion of electrons to directions parallel to amagnetic field, this direction may be controlled by varying thedirection of the eld.

Accordingly, it may be stated that it is an important object of thisinvention to provide a pair of crossed magnetizing coils within which islocated a cathode and an arrangement of anodes, the distribution ofelectron current to the anodes being controlled by controlling thedirection of the magnetic field, and the latter in turn being controlledby the ratio of the magnitudes of the currents in the two coilsindependently of the individual amplitude of these currents.

In the reception of frequency or phase modulated carrier wave energy,and which generically may be referred to as angular velocity-modulatedcarrier wave energy, it has been the practice in the past to utilize anamplitude modulation limiter prior to the frequency modulation detector.The purpose of the amplitude limiter has been to minimize the effect ofnoises, undesirable impulses external to the receiver and other wellknown effects.

Another important object of this invention is to provide a method ofreceiving angular velocity-modulated carrier wave energy whereinamplitude limitation prior to the detector is not employed, but in placethereof, and subsequent to the detection of the wave energy, there isprovided an audio frequency output which, over a large range ofamplitudes, is substantially independent of the amplitude of the radiofrequency input energy to the receiving system.

Still other objects of my invention are to improve generally theoperation of frequency modulation receivers, and more especially toprovide current magnitude ratio-controlled electron discharge deviceswhich are reliable and eicient, as well as economical to construct.

The novel features which I believe to be characteristic of my inventionare set forth with particularity in the appended claims; the inventionitself, however, as to both its organization and method of operationwill best be understood by reference to the following description takenin connection with the drawing in which I have indicateddiagrammatically several circuit organizations whereby my invention maybe carried into effect.

In the drawings:

Fig. l shows a schematic diagram of a frequency modulation receiverembodying one form of my invention,

Fig. 2 shows in lateral section a modication of the currentratio-controlled amplifier,

Fig. 3 is a longitudinal section through the amplifier of Fig. 2,

Fig. 4 shows another form of current ratiocontrolled electron dischargedevice,

Fig. 5 is a section on line 5-5 of Fig. 4 looking in the direction ofthe arrows,

Fig. 6 shows one form of anode configuration useful in the device ofFig. 4,

Fig. 7 is the anode current response characteristic for the anodes ofFig. 6,

Fig. 8 shows a modified form of anode configuration,

Fig. 9 is the anode current characteristic for the anodes of Fig. 8.

Referring, now, to the system of Fig. 1, there is shown an electrondischarge device which I have designated as a current magnituderatiocontrolled amplier. The device generally comprises an evacuatedglass envelope l which has a relatively constricted portion housing anelectron emission element, or cathode, 2. The flared portion of envelopeI houses at the broad end thereof a pair of spaced hollow collectorelectrQQlSS 3 and 4. Between these electrodes is posi- 3 tioned anelectrode 5. The electrodes 6, 'I and 8 are spaced in succession alongthe electron stream 9 to cause the stream to act as a beam, and to focusthe beam normally upon the electrode 5. The potentiometer P suppliesdirect current voltages to the various electrodes. Thus, electrodes 3and 4 are connected to opposite ends of theprimary winding of.transformer I0. The midpoint of the primary winding is connected to thepositive terminal of the potentiometer P.

Electrode 5 is connected to a less positive point on P, while electrodesIl, 'I and are connected to points of successively less positivepotential. Cathode 2 is connected to the negative termi-nal.

Any desired form of heater element `may be used for the cathode. Thedevice described thus far comprehends the elements within the tubeenvelope. A pair of crossed annular coils II and I2 are provided at apoint of the envelope such that a magnetic control field is set up whichwill control the electron beam 9. The coils I I and AI2 are suppliedwith the currents whose lmagnitude Yratio is 'to be indicated at theoutput Ill.

The tilted coils II and I2 produce a magnetic field whose directiondepends on the ratio of the magnitudes of currents. liowing through thecoils, but not ron their individual amplitudes. The electron `stream 9can flow only in the direction of the field, if the latter is strongenough. 'The energizing currents flowing through coils I I and I2 may bederived from any ,desired sources of high frequency current whose ratiois to be determined. By way of illustration, and as one object of myinvention, the current sources are shown as consisting of a pair ofseparate discriminator-recti- 1 fier networks I3 and Ill.

The networks I3 and I4 may correspond to the back to back detectors forfrequency modulated (FM) carrier waves which are well known in the art.These networks may be tuned to the operating intermediate frequency (I.F.) Value where the receiver is of the superheterodyne type. Thecircuits of such a'receiver are too well known to lrequire detaileddescription. In the case of a frequency modulation receiver of thesuperheterodyne type, there may be applied, for example, signals whosemean frequency lies in a range of 42-50 megacycles (mc), the presentlyassigned FlVI band. The frequency deviation i-s over a permissible rangeof 150 kilocycles (ka). However, the selector circuits are made wider sothat the entire modulation-representative deviations will be applied tothe discriminator networks thereby reducing distortion and the effectsof noise. For

example, at the discriminator the pass band width can be 200 kc.

The discriminator-rectifier networks I3 and I4 may be of the typewherein network I3 is a rectier having a resonant input circuitolf-tuned to one side of the center, or mean, frequency in excess of 75kc., while network I4 may be a second rectifier whose resonant inputcircuit is olf-tuned to the opposite side of the center frequency inexcess of 75 kc. Thus, as the FM signal energy from the I. F. amplifier(which may be tuned to an I. F. chosen from 3 to 15 mc.) is applied tothe off-tuned circuits, there will be produced in the rectier outputcircuits the modulation currents corresponding to the frequencydeviations of the carrier. The outputs of the rectiers consist of twocurrents, the ratio of whose amplitudes is varied in response tofrequency variation of carrier. In place of the off-tuned discriminatorthere may be used a discriminator of the type shown by S. W. Seeley inhis U. S... Patent N9.

2,121,103, granted June 21, 1938. This type USGS a center-tuned resonantcircuit to produce two alternating currents which vary differentially asthe frequency is varied.

If no amplitude modulation were present in the FM waves, the output ofnetworks I3 and I4 could be combined by means of a' transformer toprovide a single output containing lmodulation frequency currentscorresponding to the frequenlcy deviations. However, if amplitudemodulation exists on the carrier wave, and which modulation may be Ydueto noise and other extraneous impulses, the amplitude modulation willalso appear in the transformer output to a greater or lesser extentdepending upon how far the carrier frequency has been deviated from thecondition of equal output currents from the two detectors.

In the past it has been proposed to overcome this interfering output,due to amplitude modulation, by inserting some form of amplitude limiterahead of the discriminator. In my present invention I overcome `thedifficulty by eliminating a special limiter aheadof the discriminatori,and using instead the presently-disclosed current magnituderatio-controlled amplifier. The output of the latter depends upon theratio, and variations in ratio, of the magnitudes 0f two input currents,and not `upon their individual amplitudes. The cathode ray tube shown inFig. l is purely illustrative. It -is somewhat like the devices shown inmy .following patents: U. S. Patent No. 1,850,104; U. S. Patent No.1,938,331; U. S. Patent No. 1,986,632; U. S. Patent No. 1,988,621; U. S.Patent No. 2,066,037; U. S, Patent No. 2,202,376; U. S. Patent No.2,138,162; U. S. Patent No. 2,247,234.

However, in the present device the electron stream is magneticallydeflected by means of 'a magnetic field strong enough vto constrain themotion of the electron stream substantially parallel to the magneticfield. It is more or less known in the art that electrons can be given asubstantial movement only in directions parallel to the magnetic fieldwhen the latter is strong enough. This is the phenomenon used inconnection with magnetic focussing of electron beams. By passing theoutput currents of networks I3 and I4 through a pair of respectivecrossed magnetizing coils II and I2, there may be produced `a magneticfield whose direction is dependent completely upon the magnitude ratioof currents flowingthrough the two coils. If this magnetic eld is strongenough in proportion to the kinetic energy of the moving electrons, theelectron stream must take a direction substantially parallel to thefield. Hence, modulations in the ratio of the two currents controlalmost completely the distribution of electron current between theoutput anodes. Since the electron current is constant and itsdistribution between the anodes depends only upon the ratio 0f themagnitudes of the currents in the coils, and not on the individualamplitudes of these currents, the device functions to eliminatesubstantially all effects of amplitude modulation of the receivedcarrier energy.

By changing the magnitude ratio of the currents flowing through coils IIand l2 the beam 9 can be moved from the predominantly central positionon electrode 5 to either collector 3 or e. The electrode 5 is intendedto reduce flow of wasteful currents between the anodes, due to secondaryemission, when the anodes have a substantial difference in potential.The cup shape of the anodes has the same purpose of sponsecharacteristics.

`of the coils.

Asuppressing secondary emission by lcausing elec- `trons to strike inthe cups where there is little electric field for drawing out secondaryelectrons. The secondary emission can cause wasteful loading of theoutput circuits and distortion in re- If the coil currents change byequal ratios, there occurs substantially no movement of the beam. Thecollectors 3 and 4 catch the electron stream when displaced from thenormal position. The division of current between the collectors iscontrollable by the ratio of currents in the two magnetized coilssubstantially independently of the sum of the currents The deviceprovides, therefore, one means by which there can be provided an FMreceiver having an output substantially independ- -e'nt'of the receivedcarrierr amplitude, and having an output substantially free from outputderived from amplitude modulation ci the carrier current and withoutusing an amplitude limiter.

It is possible to change the construction of the current magnituderatio-responsive device considerably, and yet secure the same result.For example, in Fig. 2 there is showny a lateral section through anelectron discharge device whose longitudinal section is depicted in Fig.3. Description of this modication will be given by concurrent referenceto both gures. The tube comprises a cylindrical evacuated envelope 2Qwhich is provided with an axial filamentary cathode 2l. A positivelybiased screen 22 surrounds the cathode; the potentiometer P againprovides the direct current potentials for the various tube electrodes.The numeral 23 designates four anodes in the shape of four segments of acylinder surrounding screen 22. An absorption electrode 24. in the formof a cylinder concentric with the segmental anodes 23, surrounds thelatter.

The tube is disposed within two crossed magnetizing coils 30 and 3i. Thecoils are represented in cross-section, and the wires thereof areschematically represented. The coils 3l! and 3| set up a magnetic iieldat right angles to the direction of the axis of the device.` The coilspro- Vduce magnetic elds in directions parallel to the plane of thepaper. The electron currents flow in similar directions, parallel to theeld. The direction of this field with respect to the dispo sition of theanodes 23 is controllable by controlling the magnitude ratio of currentsin the two coils. If the two coils carry equal currents, electrons areable to flow only in up and down directions as Fig. 2 is viewed.However, if the magnitude ratio of currents is varied so as to result ina variation in the direction of the magnetic eld, the current to onepair of diametrically opposite anodes will be increased, while thecurrent to the diametrically opposite anodes is decreased. Accordingly,diametrically opposite anodes 23 are electrically connected together,and each pair of anodes is connected to a respective end of the primarywinding of transformer lo.

Since the midpoint of the primary Winding of audio transformer Il! isconnected to the positive terminal of potentiometer P, it will be seenthat spective dlscrlminator-rectiiier networks I3 and I4, as shown inFig. 1. Accordingly, as the frequency of the received carrier current ismodulated, the distribution of currents between the pairs of anodes 23is modulated to provide an audio frequency output which is substantiallyindependent of the amplitude of radio frequency input to the FM detectorsystem.

In the arrangement shown the screen electrode 22 makes it possible tohave the electrons travel over the greater part of their path fromcathode 2| to anodes 23 at relatively low velocity. Accordingly, onlymoderate magnetic eld strength is required to control the direction ofelectron flow. The anodes are operated at much higher potential than thescreen electrode in order that it may be possible to derive largeamounts of power from the device. The arrangement shown in Fig. 2 may begiven an improved operating characteristic if there is provided a meansto hold constant total current to coils 3i! and 3l. For example,reference is made to my cor-pending patent application Serial No.423,881, led December 22, 1941, for a suitable means for maintaining aconstant current to the magnetizing coils. The advantage of constanttotal current to the two coils is that there is eliminated minorvariations in response characteristics of the device due to variationsin concentration of the electron stream which could be brought aboutfrom variations in the total strength of the magnetic field.

In Figs. 4 and 5 I have shown a further modiiication of a currentmagnitude ratiocontrolled device in which the distribution of electroncurrents between tWo sets of anodes is controlled by means of thedirection of the magnetic field. The direction is, in turn, controlledby the magnitude ratio of currents in the crossed control coils. In themodication of Figs. 4 and 5 the crossed magnetizing coils are not shown,because it can readily be seen from Fig. 2 that the modication of Fig. 5differs solely in the arrangement of the electrodes. In general, thetube structure is similar to that of the modification of Fig. 2.

Referring, then, to Fig, 4 the glass envelope d0 is substantially ahollow cylinder, and has located at the axis thereof an indirectlyheated cathode which is surrounded by a screen grid 6|. The supportingrods 42 of the screen grid are shown in Fig. 5. The four segmentalanodes surround the screen grid. Catcher electrodes 43 and 44 are shownin spaced relation. One of the catcher electrodes is symmetricallylocated behind the upper pair of anodes, while the second catcherelectrode is symmetrically located behind the lower pair of anodes. Theanodes are connected in the same way as in Fig. 2. It is assumed that amagnetic iield passes through the tube which is directionallycontrollable around a direction up and down as viewed in Fig. 5. This,of course, presupposes a pair of coils arranged as coils 35i and 3| inFig. 2. With this type of tube, as the direction of the eld is variedthe distribution of currents between adjacent anodes and the catcherelectrodes is varied.

The law of response of anode currents to magnetic i'leld direction iscontrollable by controlling the design, or configuration, of the anodesegments. Suppose, for example, that one wishes to obtain anode currentscorresponding to the currents contained in a class B amplier. Then, thegap 46 between adjacent ends of anodes, where the electron streamimpinges, may be shaped as shown in Fig. 6. In Fig. 6 the eiectronstream is assumed to be normal to the plane of the sheet of the drawing.In Figs. 4 and 5 the gap between adjacent anodes is suggested, but

' is more clearly shown in Fig. 6. It will be noted that the gap issubstantially V-shaped. Such assise@ 7 Va gap l'results in a responsecharacteristic simi.- lar to that represented in Fig. 7.

If, now, it isdesired to secure -a .response characteristiccorresponding to 'a class A amplifier, then the `gap between adjacentedges of anodes may be made substantially as shown in Fig. 8. In thiscase `the gap is Yan inclined slit `whose vlopposed edges are parallel.VThe resulting response characteristic is shown lin Fig. 9. To see Whythe electrode conflgurationsof Figs. 6 and .8 .give the indicatedresponse characteristics consider that the electron beam, enclosed bythe kdotted lines, moves from right 'to left in response to change indirection voi the vmagnetic `field, and that the flow'of current to eachelectrode is pro- ;portional to the area ofthe portion of the beam.falling on it. By using various other shapes and coniigurationsdimensions, andthe like, of the gap lbetween adjacent ends of anodes,one may `,obtain substantially any type of response charvacteristicdesired. The type of tube shown in Figs. 4 and 5 provides a mostpractical arrangement for obtaining any law of response with respect toinput control which may be desired. The structure is simple and rugged,and .the Vsensitivity should be considerable if the device is designedto operate with relatively low potential vbetween. the cathode and gridelectrode in which most of the electron stream deflection ltakes place.The anodes i5 may -t-hen be operated et any higher Vpotential forobtaining relatively high power output. The .electron eiciency of thedevice can be made quite high by so design- ,ing the cathode and screenvthat substantially all -oi the yemission from the cathode is drawn outVand forced to follow a path more or less parallel to lthe magnetic eld.

It will be understood that the catcher -elec trodes i3 and M of Figp5are connected together vand connected to a moderate potential sourcewhich is less than the anode potential source. In practice, the ycatcherelectrode potential vwould usually be as low as possible, perhaps 25 or30 volts, so as to minimize secondary emission curvrents from thecatcher back to the anodes,

By simply physically turning the tube about its axis, within .fixedfield coils, one may dinerentially bias the tube Ain one direction orthe other, Las desired. Thus, if the tube .is used in indicating currentmagnitude ratios, or as a ratio `Lcontrol device, one -may change theratios at will b-y Ephysically .rotating the tube Within the mag-.netizing field coil. Of course, if'desired, the tube .may .beleft-stationary, and the magnetizing coils may be .rotated around .theaxis of the tube.

While I have indicated and described several 4systems for carrying myinvention into eect, it will be apparent to one skilled in the art thatmy invention is by no means limited to the particular organizationsshown and described, but that many modications may be made withoutdeparting from the scope of my invention, as set forth inthe appendedclaims.

What I claim :is:

1. The method of indicating the ratio of mag- ;nitudes of two separatecurrents which -includes :the steps of initiating a flow of chargedparticles, subjecting said charged particles over a substan- ...tialportion of its path of travel to a eld whose .influence forces thecharged particles to flow.

,isubstantially only along the aXis of :the stream,

utilizing one of said currents to control one com- '.IQnent of `saidi'leld, concurrently utilizing said @ther .current to control anothercomponent of Vsaid eld having an angular relationtosaid lirst .componentwhereby the direction of s aid field is dependent upon said ratio andthepreponder- `ance of one component over the other producesa transversedeflection of said charged particles.

2. The method of indicating the ratio of lmagnitudes of two separatecurrents which includes the steps of initiating a flow of chargedparticles, subjecting said charged particles over a substantial portionof its path of travel to a eld whose n influence forces the chargedparticles to flow substantially only along the axis of the stream,utilizing one of said currents to control one 4compo,-

Vnent of-said field, concurrently utilizing said other current ktocontrol another .component'of said field having an angular relation tosaid ,rst compo.- nent whereby the direction of said field is jdependentupon said ratio and the preponderance of vone component over the otherproduces `a trans- :verse deflection of said charged particles,andcollecting said charged particles 0n spaced electrodes distributed inresponse vto said deiiection.

3. The method of Vindicating theratio ,of magnitudes of two separatecurrents which includes fthe .steps of initiating a'flow of chargedparticlessubjecting said charged particles over a substantial portion ofits path of travel toa magnetic eld whose inuence forces the chargedparticles to now substantially only ,along the `axis of fthe stream,utilizing one of said currents to control one component of said 7iield,concurrently utilizing Said other current to control vanother componentof said field having an angular relation vto Said rst component wherebythe direction ofsai'd eld is dependent upon said 4ratio and the.preponderance of one component over `the other produces a transversedeflection of said charged par.- ticles.

4. A method of securing a -response to the ratio between the magnitudesof at least vtwo alternating currents which includes the steps ofproviding an electron stream to a pair of output electrodes,

distribution of electron current to fthe electrodes by controlling thedirection vof the 'field in 1response to solely said ratio.

5. In an electronic system, a tube having at least an electron emitter,at least two spaced anodes, said emitter-.projecting an electron streamtoward the anodes, means providing a magnetic field whose influenceforces electron current -to flow only in a direction parallel to the eld`and to a point between the spaced anodes, and addi tional means forapplying to said magnetic field means at least -two alternating currentswhose magnitude lratio is solely utilized to deflect said stream.

6. The method of determining the ratioof magnitudes of two audiocurrents subject to amplitude variation which includes .the steps ofinitiating a flow of charged particles, subjecting said chargedparticles over Va-substantial portion .of its path of travel to amagnetic eld of sulicient strength to substantially suppresscomponents,of

flow at right angles to the direction vof the field,

utilizing one of said audio currents to control one 'solely said :ratiofree of said amplitude variation.

7. The method of producing a response to the ratio of magnitudes of twoalternating currents subject to amplitude variation which includes thesteps of projecting a now of charged particles. subjecting said chargedparticles over a substantial portion of its path of travel to a magneticfield strong enough to confine the fiow substantially to a directionparallel with the field, utilizing One of said currents to control onecomponent of said field, concurrently utilizing said other current tocontrol another component of said field having an angular relation tosaid first component whereby the direction of said field is determinedsolely by said ratio and the preponderance of one component over theother produces a transverse deflection of the direction of iow of saidcharged particles.

8. In a system Vfor indicating the ratio of magnitudes of two separatecurrents which comprises means for initiating a iiow of chargedparticles, means for subjecting said charged particles over asubstantial portion of its path of travel to a field which permitssubstantial flow only in a direction parallel to the field, meansutilizing one of said currents to control one component of said field,means concurrently utilizing said other current to control anothercomponent of said field having an angular relation to said firstcomponent, and the preponderance of one component over the otherproducing a transverse deflection of said charged particles.

9. In a system for determining the ratio of magnitudes of two audiocurrents subject to amplitude variation which includes an electronicdevice having a means for initiating a ow of charged particles, a pairof magnetizing coils whose planes are crossed subjecting said chargedparticles over a substantial portion of its path of travel to a magneticfield in response to the currents to form a resultant field whosedirection depends upon the ratio of the two currents, and utilizing theresultant field to control the direction of flow of charged particlessubstantially independently of field for determining the direction offlow, means applying one of said audio currents to one coil thereby tocontrol one component of said field, means applying the second currentto the second coil thereby to control another component of said fieldhaving an angular relation to said first component, the preponderance ofone component over the other produces a transverse deflection of saidcharged particles.

10. A method of indicating the ratio between the magnitudes of at leasttwo audio frequency currents subject to amplitude variation whichincludes the steps of providing an electron stream to a pair of electroncollectors, providing a magnetic field whereby substantial electroncurrent flow can take place only in the direction parallel to themagnetic field and to a point between said collectors, and controllingthe distribution of electron current to the collectors by controllingthe direction of the field in responseto solely said magnitude ratio ofsaid currents.

11. A system for indicating the ratio between the intensity of at leasttwo currents, which comprises an electron discharge device having acathode, a pair of spaced anodes, crossed magnetizing coils surroundingthe device propagating an electron stream from the cathode to a pointintermediate the anodes, said coils normally providing a magnetic fieldfor controlling the direction of iiow of th'e stream, and means applyingsaid currents separately to said respective coils thereby to control thedirection of the field and the intensity of electron current collectedby either anode as a function solely of said ratio.

12. The method of indicating the ratio of magnitudes of two separatecurrents which includes producing two angularly disposed components ofthe sum of the two currents.V

13. The method of indicating the ratio of magnitudes of two separatecurrents which comprises utilizing the currents to produce a resultantmagnetic eld the direction of which is dependent only on the ratio ofmagnitudes of the two currents, and utilizing the resultant magneticfield to determine the direction of flow of electron current in a Vacuumtube.

14. The method of utilizing the ratio of magnitudes of two separatecurrents substantially independently of their individual magnitudeswhich comprises utilizing the currents to produce a magnetic field thedirection of which is dependent only on the ratio of the magnitudes ofthe currents, and utilizing the direction of the field to controldistribution of electron current between electrodes in a vacuum tube.

l5. Means responsive to the ratio of the magnitudes of two currentscomprising magnetizing coils crossed over atan angle for producing aresultant magnetic field, means for producing a constant currentelectron stream, and means for collecting currents from the stream whosesum is constant but whose division is determined by the direction of themagnetic field.

16. In a system for obtaining currents responsive to the magnitude ratiobut not the separate amplitudes of two currents comprising means to setup a magnetic field whose direction is determined by the ratio, andmeans to utilize the direction of the magnetic field to determine thedistribution of electron current between electrodes of a vacuum tube.

17. In a system as defined in claim 16, characterized by adjustment ofthe strength of magnetic field to be great enough so that, over anoperating range of field strengths, the distribution of electron currentis nearly independent of the strength of the field.

18. The method of receiving angular-velocity modulated carrier wavessubject to amplitude variation which includes deriving from the wavestwo separate modulation currents subject to said variation, initiating aflow of charged particles, subjecting said charged particles over asubstantial portion of its path o-f travel to a field Whose influenceforces the charged particles to fiow substantially only along the axisof the stream, utilizing one of said modulation currents to control onecomponent of said field, utilizing said other modulation current tocontrol another component of said field having an angular relation tosaid first component whereby4 the preponderance of one component overthe other produces a transverse deflection of said charged particles,and translating said denection into a resultant modulation current freeof said variation.

19. The method of receiving frequency modulated carrier waves subject toundesired amplitude variation, which includes deriving from said wavestwo audio currents subject to said undesired variation, initiating aflow of charged particles, subjecting said charged particles over a sub-0 stantial portion of its path of travel to a magnetic eld of sufficientstrength to substantially suppress components of now at right angles tothe direction of the field, utilizing one of said audio currents tocontrol one component of said field,

utilizing said other audio current to control angction into a. resultantludi' current fre of said.v

ilaria lon in satijd c' dshrgv device spaced nod'es, c'r rounding the dey I n strm from the' c odejto latvpoit intermediate' the anodes, saidcoils riorrnaHyproviding' a mgf netic eid for c0n .t rc 1 linfg` thedirection Qi flow/off the stream', arid `nflirrs ,applying Saidmodulation currents Separately to s'aid respective coils tlfierejf by tocontro-11th@ directi'nfof tiigriield a-djtlje intensity of electroncurrent collected by eitl'rf anode.

CLARENCE W. HANsELI-i;

REFERENGES 'ci-TED The following Yfei'r'eric'es e' f rcord. r tiY le ofthis patent: K

UNITD STATES PATENTS- Nine Y bate L Skeuet' o'ct. 15, 194g Wagner' Nv.I2, 1940 uirier Y 2,217,774 25v 2,221,743

